AVIF image format support

[newbie-461]

TODO:

1. use dav1d to decode AVIF image
2. alpha channel / HDR to SDR support (qcms_profile_create_cicp, qcms 0.2.0 requires a higher Rust version)
3. auto add MIME to HTTP Accept header when AVIF decoder is enabled
4. x64 and sse x86 test

---

Modules are mostly copied from firefox-93.0.source.tar.xz
(update)
gfx/ycbcr
media/libyuv
media/mp4parse 0.11.5
(rust dependency)
fallible_collections
ahash

[Feodor2]

Also

1. Do not copy first junk lines "mode...."
2. Telemtry is unnecessary

[Feodor2]

More when I examine all, if many code most likely the config switch for not to build like for webrender

[newbie-461]

Ok, i will try to simplify this patch

[dainiusb]

Cleanup patch (meant to be applied on top of this PR) generated by LLM.

1. Telemetry removed — stripped all AccumulateCategorical, RecordPixiTelemetry, RecordDecodeResultTelemetry, and the AVIF histograms from Histograms.json

2. Build config switch added — MOZ_AVIF (--disable-avif), defaults ON when AV1 is enabled, gates the decoder, MIME type, and content registration independently

3. SpeedHistogram() returns Nothing()

Stats: +27 / −421 on top of the PR commit. The .patch applies cleanly on ad6e2a0.

The merge conflicts are from the original PR — it's based on an older main that has since moved mp4parse and fallible_collections to third_party/rust/. The PR needs a rebase first.
Cargo.lock / Cargo.toml drift: Dependencies have changed on main since the PR was authored.
After rebasing, the simplification patch (strip telemetry + add MOZ_AVIF switch) applies cleanly with no conflicts — I tested the 7 files it touches auto-merge fine.

0001-simplify-avif-strip-telemetry-add-MOZ_AVIF.patch.txt